Discrete Relativity?

Consider the thought experiment involving four hypothetical perfectly equidistantly juxtaposed "co-moving" observers[A,B,C,D], with a flash of light eminating from their equidistant center-point[P]:

A_________B

_____P

C_________D

The flash of light obeys what is known as Lorentz invariance, and will reach all observers[A,B,C,D] simultaniously, since they are co-moving and at rest with respect to each other.

If reality is totally discrete then the expanding circle of light that reaches all observers simultaneously has a circumference that consists of discrete Planck units, not a continuous circle described by 2*pi*radius?